Methods in mining by sublevel caving

ABSTRACT

A method in mining by sublevel caving in which in a development phase are driven haulage drifts or shafts and from said drifts or shafts are driven cross-cuts in an orebody with a spacing vertically and horizontally suitable from an economical and technical point of view, from which cross-cuts one or more longitudinal drifts are driven in said orebody, wherein said cross-cuts are driven straight through said orebody and into the rock wall at the opposite side thereof, where said cross-cuts are connected with upwardly directed ventilation shafts, and vertically adjacent pairs of discs are connected with these shafts and/or haulage drifts or shafts and associated ventilation means in such a way, that the upper disc then during the mining can be put under considerable sub-atmospheric pressure, while the lower disc can be put under suitable, comparatively moderate positive pressure by entering fresh air, whereby an essentially continuous mining of said orebody is allowed.

United States Patent Kristoffersson et al.

[451 Dec. 26, 1972 Primary Examiner-Ernest R. Purser Attorney-Sommers & Young [57] ABSTRACT A method in mining by sublevel caving in which in a development phase are driven haulage drifts or shafts and from said drifts or shafts are driven cross-cuts in an orebody with a spacing vertically and horizontally suitable from an economical and technical point of view, from which cross-cuts one or more longitudinal drifts are driven in said orebody, wherein said crosscuts are driven straight through said orebody and into the rock wall at the opposite side thereof, where said cross-cuts are connected with upwardly directed ventilation shafts, and vertically adjacent pairs of discs are connected with these shafts and/or haulage drifts or shafts and associated ventilation means in such a way, that the upper disc then during the mining can be put under considerable sub-atmospheric pressure, while the lower disc can be put under suitable, comparatively moderate positive pressure by entering fresh air, whereby an essentially continuous mining of said orebody is allowed.

10 Claims, 5 Drawing Figures PTNTD nicas |972 SHEET 1 Uf 3 INVENTORS Harry Krisroffersson Sune Torsten Henriksson BY M fm ATTORNEYS DEC 2 6 i912 snm s or a FIG. 3

INVENTORS Harry Krsfofersson Sune Torsten Henriksson BY muy A T TORNE YS METHODS IN MINING BY SUBLEVEL CAVING The present invention relates to a method in mining by sublevel caving in which in a development phase, on one side of the orebody to be mined, i.eY the "haulage wall side" or, in case of an inclined orebody, preferably the foot wall side, are driven haulage drifts or shafts, for example haulageways inclined relative to the horizontal plane, and from said drifts or shafts are driven crosscuts in said orebody with a spacing vertically and horizontally suitable from an economical and technical point of view, from which cross-cuts one or more longitudinal drifts are driven in said orebody.

Applications of the sublevel caving hitherto used in mining have all had the same disadvantage in common with most other mining methods, viz. the difficulties to provide an acceptable ventilationA Usually the loading drifts have been put under negative pressure or suction and consequently via the caved materials sucked up fresh air coming from ventilation shafts or headings. With increasing depth of the mines, this ventilation becomes more and more difficult, and attempts have been made to avoid this by blowing, instead or in addition, pressurized fresh air through the caved materials. However this has not either proved to be satisfying. There are of course possibilities to introduce particular ventilation ducts or the like in the headings, but this, however, is space-consuming,

lnvestigations recently made concerning the possibilities to rationalize the mining to an important extent have in fact led to a strongly increased need for providing a greatly improved and most satisfying ventilation of the drifts of mines, particularly the loading drifts This becomes most of all conspicuous in those cases, when vehicles with internal combustion engines are to be used for loading and transport, principally so-called "trackless operation," If a sufficently great number of loading and transport vehicles with internal combastion engines are to be used simultaneously in the working for providing a really rational operation, the ventilation will be completely inadequate with the present measuresA Therefore, the fact can be established that at present, it is almost solely the ventilation problem that completely stops the possibilities of obtaining a really rational and continuous mining, in any case in the sublevel caving.

The main object of the present invention is to provide a method, which actually eliminates the abovementioned difficulties and which is essentially distinguished in that said cross-cuts are driven straight through said orebody and into the rockwall at the opposite side thereof, i.e. the "ventilation wall side" or in case of an inclined orebody, preferably into the hanging wall side, where said cross-cuts are connected with upwardly directed ventilation shafts, and that vertically adjacent pairs of discs are connected with these shafts and/or haulage drifts or shafts and associated ventilation means in such a way, that the upper disc, the drilling disc, during the mining can be put under considerable sub-atmospheric pressure for exhaustion of air and gases during drilling and blasting while the lower disc, the loading disc, can be put under suitable, comparatively moderate positive or over-atmospheric.` pressure by entering fresh air, and be utilized for loading with only short interruptions or breaks about the time for blasting in the drilling disc above, whereby an essentially continuous mining of said orebody is allowed.

Owing to the invention a method in mining by sublevel caving is provided, in which actually can be obtained such favorable and almost satisfactory ventilation conditions in a very easy way, that on the drilling discs is allowed a very large efficiency of work owing to the fact that the stops or breaks for ventilation only need to be of short duration in connection with blasting, while the drilling soon can be resumed again and be continued without other breaks. Owing to the fact that the loading dises are under negative pressure, the blasting gases are effectively prevented from moving downwards from the drilling disc situated above at every blast, so that breaks in loading work on the loading disc are necessary only during periods required for security reasons in connection with each blast. Owing to the fact that the ventilation air blown into the loading disc under positive pressure has a very short way to pass through the caved material up to the drilling disc situated above, which drilling disc is subjected to intensive evacuation or suction, the ventilation and the change of air is facilitated to a great extent and the caved materials hardly at all can constitute any appreeiable obstruction for the passage of air.

After having successfully solved the ventilation problem in this way, it can also be noted that the invention in addition results in a number of favorable secondary effects relating to mining technique. ln addition to the strongly increased ore loading rate which of course is made possible, the utilization rate of the machines used will also essentially increase. A loading machine, which at present in sublevel caving is used hardly more than 8 percent of the operation time, can now be used for about 7() percent or more of the operation time, Owing to the method according to the invention it is also possible to use other drilling equipments, which makes it possible to drill in a more rational and timesaving way, thereby avoiding superfluous boulderblasting, which otherwise is very expensive. lt is also possible to adapt drilling and blasting in such a way, that a desirable, relatively fine lump size is obtained. Also other advantages are obtained, which, however, will be further evident below.

By the way of example the invention is further described below with reference to the accompanying drawing in which:

FIG. la shows a sectional elevational view and FIG. lb a sectional plan view of ari orebody during mining with the method according to the invention,

FIG. 2 is a sectional plan view through said orebody similar to FIG, Ib but at the end of the development phase required prior to mining,

FIG. 3 shows a sectional end view through said orebody at substantially the same period of said development phase as FIG. 2, and

FIG` 4 finally shows a sectional elevational view in the longitudinal direction of said orebody at opening or mining.

ln carrying out the method according to the present invention, it is generally begun with a development phase, In the embodiment illustrated in the drawings the development phase is started on one side of the orebody to be mined, i.e. "the haulage wall side" T or in case of an inclined orebody preferably the foot wall side, by driving haulage drifts, preferably constituting haulage ways inclined relative to the horizontal plane. Said haulage ways which are intended for transport with ordinary trackless vehicles are preferably inclined in the ratio l:l0. lt must be pointed out however that the method according to the present invention naturally is not limited to trackless vehicles only for transport of the ore. The method can also be used advantageously in case vertical or upwardly directed haulage shafts for hoisting of the ore are provided, which shafts are suggested on the drawing.

In the last mentioned case with inclined haulage headings or ways, crosscuts are driven in the orebody with a spacing vertically and horizontally suitable from an economical and technical point of view.

The spacing between the cross cuts is first of all dependent upon the vertical distance at which discs are to be placed from each other in the subsequent disc mining, but is also naturally dependent upon the selected degree of inclination of the haulage ways and other parameters. According to the invention said cross-cuts arc now driven straight through the orebody and into the rockwall on the opposite side of the orebody, viz the ventilation wall side" or, in case of an inclined orebody, into the hanging wall side. The cross-cuts are situated vertically above each other are connected in the rockwall with upwardly directed ventilation shafts.

More precisely it is proceeded in such a way, that from the inclined haulage way 30, where this comes down to a certain level and a disc in sublevel caving is to be located, a cross-cut designated l in the drawings, is driven through the orebody and out into the rock wall V at the opposite side, where this cross-cut thus is connected with a ventilation shaft 2, which is driven upwardly. At this point on this part of the inclined haulage way immediately in front of the abovementioned disc level, where the next above situated disc for the disc mining is to be positioned there is made a short cut 3 in the the orebody, and from there is driven a longitudinal drift 4 in the orebody at this level out to a point above the first cross-cut l, where a new cross-cut 6 is driven, which also is driven straight through the orebody and out into the rock wall at the opposite side, where this new cross-cut likewise is connected with the upwardly directed ventilation shaft 2. These two last mentioned discs are therefore situated vertically directly above each other and of these discs the upper one B is utilized for drilling and the lower one L for loading according to the method of the invention, which will bc closer described below.

Suitably, the above-mentioned haulage way 30 is rcdirected at the cross-cut l on the level for the loading disc L and is continued downwardly in the opposite direction until it reaches a depth corresponding to the next pair of discs located below each other, where a new cross-cut is to be made. This cross-cut 7 is made in the same way as the cross-cut l and is connected with an other upwardly directed ventilation shaft 2, which is driven upwardly. Half way along this new part of the haulage way at the level of the nearest above-situated disc a cut 8 is made in the same way in the orebody and a longitudinal drift 5 is driven within the latter up to a point above the last-mentioned cross-cut, where a new cross-cut 9 is opened in the same way and driven through the orebody and into the rock wall V and into .MIZ

connection with the other ventilation shaft 2. From all these cross-cuts are then conventionally opened one or more longitudinal drifts l0, preferably mutually parallel, at each disc level, said drifts being illustrated with dashed lines on the drawings.

ln this connection, however, it must bepointed out, that the sequence of the different steps in the abovementioned development phase, naturally is not critical for the basic idea of the present invention but can be modified to a great extent by those skilled in the art dependent on present needs and circumstances. It should also be observed, that this development phase advantageously leads to an standardized mining disposition of module type where naturally multiple applications easily can be utilized. As alternative or complement to the haulage way 30, haulage shafts 32 likewise can be arranged.

After the above-stated system of crosscuts and longitudinal drift has been prepared to the necessary extent and the development phase thus is finished, the mining or opening of the mining front F is to be done, and this is perferably carried out in the longitudinal drifts in the orebody at a place substantially half-way between two ventilation shafts. According to the invention, the upper disc in each pair then is used as drilling disc and the lower one as loading disc. For this purpose, the two discs are connected with ventilation shafts and/or haulage headings or shafts and associated ventilation means is such a way, that the upper disc in each pair, i.e. the drilling disc, during the mining can be put under considerable atmospheric pressure for evacuating air and gases, while the disc is worked by drilling and blasting, and the lower disc in the same pair, i.e. the loading dise, can be put under suitable, comparatively moderate positive or over atmospheric pressure by entering fresh air.

More precisely, this is carried out preferably in that way, that on the loading disc L in the cross-cuts thereof adjacent the haulage wall side T is installed a pressure fan device 20, whereas the connection of the same crosscuts with the ventilation shafts 2 in the ventilation wall side V is closed by a one way ventilation port 22. ln the drilling disc B a suction fan device 24 of greater capacity than the pressure fan device is placed in the connection of the cross-cuts with the ventilation shaft 2 of the ventilation wall side V, whereas in the connection of these cross-cuts with the haulage wall side T is arranged a one-way ventilation port 26, a so-called suction port. Because of this, it will thus be achieved a very good ventilation effect as previously stated and considered a very important advantage, said effect even being so satisfactory, that the loading disc l.. almost continuously can be employed for loading by loading and haulage machines driven by internal combustion engines, while drilling disc B is so effectively ventilated, that the work therein can be carried out almost con` tinuously. Thus, the only breaks necessary are those which must be observed for security reasons at the time for each blast.

Having knowledge of the difficulties described above and up to now considered as unavoidable to obtain a satisfying ventilation, it is easy to understand the great possibility that are opened owing to the ventilation, that is achieved by the method according to the present invention. lt is not only possible to obtain an essentially increased ore production rate, but the machine fleet can also be utilized in a still much more rational way than before at the same time as many other advantages are obtained as secondary effects. Among these preferably can be mentioned, that better machines can be used for making the drilling holes in the drilling disc and also arrange the location of said holes in such a way, that a more rational blasting with also smaller lump size can be obtained. The most surprising fact with the method according to the invention, however` is that a satisfactory ventilation is obtained to such an extent, that the mining can be carried out practically continuously with only short breaks despite both exhaust gases from the internal combustion engines of the machine fleet and the gases from the blasting. The extended ventilation breaks otherwise necessary thus now can be reduced to very short breaks. Another advantage in the method is also that largescale mining can be carried out with a plurality of loading sites, whereby a more concentrated mining and an increased mine-sinking becomes possible.

Finally` it is only to point out again, that the invention naturally can be widely modified and varied by those skilled in the art with-in its scope, as it is deflned in the accompanying claims.

We claim:

1. A method of mining by sublevel caving comprising the steps of forming at least two vertically directed ventilation shafts disposed in spaced relation to one another within a rockwall adjacent an orebody, driving a plurality of horizontally directed cross cuts extending in vertically spaced relation to one another from said rockwall and from said ventilation shafts into said orebody, driving a plurality of longitudinal drifts extending horizontally into said orebody from each of said cross cuts respectively to form a plurality of horizontally extending discs vertically spaced from one another in pairs, the upper one of each of said pair of discs being utilized as a drilling disc during subsequent mining operations and the lower one of each of said pair of discs being utilized as a loading disc during said subsequent mining operations, applying fresh air at a pressure in excess of atmospheric pressure to the lower, loading disc of each of said pair of discs, and applying a sub-atmospheric pressure to the upper, drilling disc in each of said pair of discs to exhaust air and gases produced as a result of drilling and blasting during mining operations.

2. The method of claim l including the step of driving vertically extending haulage shafts communicating with said cross cuts.

3. The method of claim l including the step of driving a plurality of drifts into said orebody extending in parallel, substantially horizontal relation to one another from each of said discs.

4. The method of claim l wherein said mining operations comprise opening said orebody at a position substantially equally spaced from said two ventilation shafts.

5. The method of claim l including the step of driving a further plurality of horizontally directed, vertically spaced cross cuts into said orebody at positions between said ventilation shafts, each of said discs extending between one of said first-mentioned plurality of cross cuts and one of said further plurality of cross cuts.

6. The method of claim 5 Including the step of driving a plurality of inclined haulage drifts into said orebody, each of said haulage drifts communicating at its opposing ends with a pair of said first-mentioned cross cuts and communicating, at a mid-portion of its extension, with one of said further plurality of cross cuts.

7. The method of claim l including the step of driving a plurality of inclined haulage drifts into said orebody, each of said haulage drifts communicating at its opposing ends with a pair of said cross cuts.

8. The method of claim 7 wherein said fresh air is applied by a pressure fan placed adjacent the cross cut between each of said loading discs and one of said haulage drifts, and a one-way ventilation port is placed adjacent the cross cut between each of said loading discs and one of said ventilation shafts.

9. The method of claim 8 wherein said sub-atmospheric pressure is applied to each of said drilling discs by a suction fan placed adjacent the cross cut between each of said drilling discs and one of said ventilation shafts, and a one-way ventilation port is placed adjacent the cross cut between each of said drilling discs and one of said haulage drifts.

l0. The method of claim 9 wherein said suction fari has a greater capacity than said pressure fan. 

1. A method of mining by sublevel caving comprising the steps of forming at least two vertically directed ventilation shafts disposed in spaced relation to one another within a rockwall adjacent an orebody, driving a plurality of horizontally directed cross cuts extending in vertically spaced relation to one another from said rockwall and from said ventilation shafts into said orebody, driving a plurality of longitudinal drifts extending horizontally into said orebody from each of said cross cuts respectively to form a plurality of horizontally extending discs vertically spaced from one another in pairs, the upper one of each of said pair of discs being utilized as a drilling disc during subsequent mining operations and the lower one of each of said pair of discs being utilized as a loading disc during said subsequent mining operations, applying fresh air at a pressure in excess of atmospheric pressure to the lower, loading disc of each of said pair of discs, and applying a sub-atmospheric pressure to the upper, drilling disc in each of said pair of discs to exhaust air and gases produced as a result of drilling and blasting during mining operations.
 2. The method of claim 1 including the step of driving vertically extending haulage shafts communicating with said cross cuts.
 3. The method of claim 1 including the step of driving a plurality of drifts into said orebody extending in parallel, substantially horizontal relation to one another from each of said discs.
 4. The method of claim 1 wherein said mining operations comprise opening said orebody at a position substantially equally spaced from said two ventilation shafts.
 5. The method of claim 1 including the step of driving a further plurality of horizontally directed, vertically spaced cross cuts into said orebody at positions between said ventilation shafts, each of said discs extending between one of said first-mentioned plurality of cross cuts and one of said further plurality of cross cuts.
 6. The method of claim 5 including the step of driving a plurality of inclined haulage drifts into said orebody, each of said haulage drifts communicating at its opposing ends with a pair of said first-mentioned cross cuts and communicating, at a mid-portion of its extension, with one of said further plurality of cross cuts.
 7. The method of claim 1 including the step of driving a plurality of inclined haulage drifts into said orebody, each of said haulage drifts communicating at its opposing ends with a pair of said cross cuts.
 8. The method of claim 7 wherein said fresh air is applied by a pressure fan placed adjacent the cross cut between each of said loading discs and one of said haulage drifts, and a one-way ventilation port is placed adjacent the cross cut between each of said loading discs and one of said ventilation shafts.
 9. The method of claim 8 wherein said sub-atmospheric pressure is applied to each of said drilling discs by a suction fan placed adjacent the cross cut between each of said drilling discs and one of said ventilation shafts, and a one-way ventilation port is placed adjacent the cross cut between each of said drilling discs and one of said haulage drifts.
 10. The method of claim 9 wherein said suction fan has a greater capacity than said pressure fan. 